1. Field of the Invention
This invention relates to an automotive passenger restraint and protection apparatus for automotive vehicles such as automobiles, which uses an electric retractor for retracting and protracting a seatbelt for protection of an occupant (driver or passenger), and also relates to a seatbelt retraction and protraction amount-detecting device.
2. Prior Art
Conventional automotive passenger restraint and protection apparatuses are operable upon a large deceleration of the automotive vehicle such as a collision to restrain an occupant by means of a seatbelt to prevent him from being thrown out of his seat and hence protect him from danger.
Conventional automotive restraint and protection apparatus include a type provided with a seatbelt retractor for retracting or winding a seatbelt. The seatbelt retractor is generally provided with bias force-imparting means such as a spiral spring which always biases a reel shaft (takeup shaft) on which the seatbelt is wound, in a retracting or winding direction. The seatbelt is wound up on the reel shaft due to the bias force provided by the bias force-imparting means when the seatbelt is not mounted on the occupant, and is protracted or withdrawn against the bias force to fasten or restrain the occupant when the seatbelt is mounted on the occupant.
The seatbelt retractor is provided with emergency locking means which is normally actuated upon a large deceleration of the vehicle as mentioned above, to impede rotation of the reel shaft in the seatbelt protracting direction, so as for the seatbelt to surely restrain and protect the occupant.
According to the conventional automotive passenger restraint and protection apparatus, however, to mount the seatbelt onto the occupant, the occupant has to protract the seatbelt against the bias force of the bias force-imparting means, which requires the occupant to exert some force to protract the seatbelt. As a result, a weak occupant who has degraded physical ability, such as that which occurs with advanced-age, takes a long time to mount the seatbelt onto his body.
Further, there can be a case that the occupant feels uneasy while he wears the seatbelt since he feels a sense of oppression owing to the bias force of the bias force-imparting means.
Moreover, the conventional automotive passenger restraint and protection apparatus is not provided with means for warning the occupant of danger to be caused by a doze and a collision.
A further disadvantage with the conventional apparatus is that an alien substance can become attached to the seatbelt after a long term use, which causes an increased friction between the seatbelt and a through anchor associated therewith, leading to insufficient retraction of the seatbelt.
The conventional automotive passenger restraint and protection apparatus has another disadvantage that when the occupant has protracted the seatbelt without the intention of wearing the same, it can happen that the seatbelt cannot be retracted until a certain time period elapses. Thus, the seatbelt cannot be quickly retracted against the occupant's desire.
Further, in the conventional automotive passenger restraint and protection apparatus, in retracting the seatbelt into its extreme retracted position, if the occupant intentionally stops the seatbelt at a position apart from his body and then judges that the seatbelt has reached its extreme retracted position, the seatbelt can be set in position in an abnormally loosened state.
Further, in the conventional automotive passenger restraint and protection apparatus, when the occupant looks back for parking the vehicle while moving his body to protract the seatbelt, the seatbelt is wound back or retracted into the extreme retracted position after the completion of protraction of the seatbelt, which gives a feeling of unnaturalness to the occupant.
Furthermore, when the occupant's body is not in a proper position for driving the vehicle, that is, his body is not facing forwardly of the vehicle, the seatbelt can be wound up into the extreme retracted position, based upon which position the occupant is given a predetermined amount of looseness of the seatbelt, which can result in an inappropriate amount of looseness of the seatbelt being given to the occupant to make him feel uncomfortable.
In the conventional passenger restraint and protection apparatus, in the event that the seatbelt becomes locked when a motor for driving the seatbelt is rotated in the direction of the seatbelt being protracted, no force is acted upon the seatbelt to retract the same, so that the seatbelt is kept in the locked state, which can make it impossible to protract the seatbelt unless a condition is newly set for the seatbelt to be retracted.
The condition for the seatbelt to be retracted is set in the cases where the vehicle is suddenly braked, the seatbelt is taken off or disconnected from the occupant's body, and it is judged that the occupant's vehicle is about to collide with some object, by a collision prediction system, for example.
FIG. 83 is a timing chart showing another example of the relationship between driving forces of a reel shaft for retracting and protracting a seatbelt onto and from the reel shaft, an urging force which the occupant receives from the seatbelt, and the seatbelt retracting and protracting speeds of the reel shaft in the conventional automotive passenger restraint and protection apparatus.
First, when attaching of the seatbelt to the occupant's body is detected, retraction of the seatbelt onto the reel shaft is started by the reel shaft with a constant seatbelt retraction driving force, and this retraction is continued until the retraction of the seatbelt reaches its limit (time period t20). During this retraction, the urging force which the occupant receives from the seatbelt gradually increases while the retracting speed of the seatbelt onto the reel shaft gradually decreases.
Thereafter, when the retraction of the seatbelt has reached its limit (time point c), the retraction of the seatbelt by the reel shaft is stopped, and then protraction of the seatbelt can be effected due to a restitution force against the bias force of the spiral spring, etc., that is, a restitution force of the occupant's body and clothes urged by the seatbelt. During this protraction, the acceleration of protraction of the seatbelt from the reel shaft increases.
Since when the retraction of the seatbelt by the reel shaft reaches its limit after the attaching of the seatbelt and the retracting motion stops, however, the seatbelt is suddenly returned in the direction in which the urging force is weakened due to the restitution force of the occupant's body and clothes urged by the seatbelt, the acceleration of protraction of the seatbelt from the reel shaft suddenly increases and can exceed a threshold value required for locking the protracting motion of the seatbelt, so that the protracting motion of the seatbelt can be locked by a seatbelt locking mechanism. As a result, the urging force that the occupant receives from the seatbelt cannot be relieved after a time point when it assumes a large value (time point d) (time period t21).
An automotive passenger restraint and protection apparatus is also already known, which is provided with an airbag device for restraining an occupant through expansion of an airbag, a belt pretentioner for restraining the occupant by suddenly retracting a seatbelt, an airbag and pretensioner controller for controlling actuation time and expansion pressure of the airbag and actuation time and seatbelt-pulling force of the pretensioner, and a sensor for detecting negative acceleration acted upon the occupant upon a collision of the automotive vehicle.
When negative acceleration acted upon the occupant is detected by the sensor upon a collision of the automotive vehicle, a signal indicative of the negative acceleration from the sensor is delivered to the airbag and pretensioner controller, which in turn controls the actuation time and expansion pressure of the airbag and actuation time and seatbelt-winding force of the pretensioner, whereby the airbag and the pretensioner are actuated.
In the known automotive passenger restraint and protection apparatus, however, the actuation time and expansion pressure of the airbag are controlled by the airbag and pretensioner controller upon a collision of the automotive vehicle, irrespective of the protracting speed of the seatbelt. Consequently, for example, when it is judged by the controller that the actuation times for actuating the airbag and the pretensioner should be set to longer values, the airbag and the pretensioner are actuated with the longer actuation times even in the event that the protracting speed of the seatbelt is so high that the occupant can collide against equipment within the compartment.
Further, when it is judged by the controller that the expansion pressure for actuating the airbag should be set to a higher value, the expansion pressure of the airbag cannot be changed according to the protracting speed of the airbag even in the event that the protracting speed of the seatbelt is so high and the occupant is restrained by the airbag expanded under such a higher expansion pressure that the occupant can directly receive a large impact applied to the vehicle.
Also, conventionally there is known a mechanism called “EA mechanism” (load limiter) which has a function of causing the reel shaft to rotate in the direction of protracting the seatbelt when a tension in excess of a prescribed value is applied to the seatbelt immediately after a collision of the automotive vehicle, so as to control the tension to or below the prescribed value (hereinafter referred to as “the EA function”). The EA function is terminated when the seatbelt is protracted by a certain length after the EA function is made effective. That is, the EA function is carried out irrespective of the degree of magnitude of collision of the automotive vehicle. Consequently, in the event of a strong collision of the automotive vehicle, for example, the EA function can be terminated even at a time point when it is desired that the same function should be still exhibited, whereby a sudden impact can be applied to the occupant after termination of the EA function, which can result in insufficient effective absorption of an impact acted upon the occupant. On the other hand, in the event of a weak collision of the automotive vehicle, a tensile strength in excess of the prescribed value is not applied to the seatbelt, so that the EA function is not made effective, whereby impact absorption cannot be obtained.
Fault diagnosis of the seatbelt locking mechanism has conventionally been carried out through a determination by the occupant or the like as to whether the seatbelt can be actually retracted and protracted, or as to whether the seatbelt can be locked in position by suddenly protracting the same.
This manner of fault diagnosis, however, cannot always achieve accurate fault determination of the seatbelt locking mechanism.
Further, in the conventional automotive passenger restraint and protection apparatus, when the occupant with the seatbelt not mounted on his body pulls out the seatbelt without the intention of attaching the same to his body, immediately then gets off the vehicle and closes the door, the seatbelt is not retracted within a short time period, so that the seatbelt can be caught in the door to be damaged. Also, when during parking of the automotive vehicle, the seatbelt is pulled out and attached to a baggage or the like (into the mounted state of the seatbelt) and then, in this state the door is closed, the seatbelt can be also caught in the door if the seatbelt is then unnecessarily loosened.
An automotive passenger restraint and protection apparatus is also already known, which detects a possibility of collision of the automotive vehicle based upon the distance between the occupant's vehicle and a preceding vehicle, and gives an alarm to alert the occupant to the danger of collision based upon the detection result, so as to prevent a traffic accident.
An example of the apparatus having such a warning function is disclosed by Japanese Laid-Open Utility Model Publication (Kokai) No. 6-71333, which is adapted to intermittently increase or decrease the fastening force of the seatbelt when it is detected that the distance between vehicles becomes shorter than a predetermined safety distance.
In the known automotive passenger restraint and protection apparatus, however, the control of intermittent increase or decrease of the fastening force is carried out in a monotonous manner irrespective of the degree of possibility of expected danger so long as the distance between vehicles is less than the safety distance. Consequently, when the degree of possibility of expected danger is low, the above control can be annoying to the occupant, whereas when the degree is high, the same control is insufficient and unsatisfactory to him. Thus, the above control is not fully effective to warn the occupant of expected danger.
There is also conventionally known an automotive vehicle having a function of storing, upon a collision of the automotive vehicle, the value of acceleration caused by the collision and the collision speed, in order to utilize the stored data in clearing up the cause of the accident, for example.
In the known automotive vehicle, however, it is the value of acceleration caused by the collision and the collision speed that are stored, but not information (parameters) related to the automotive passenger restraint and protection apparatus. Therefore, it is not easy to judge whether the automotive passenger restraint and protection apparatus properly operated upon the collision, and how the occupant behaved just before and/or after the collision, for example.
An automotive passenger restraint and protection apparatus is also known, which is provided with an electric retractor which rotates a reel shaft by means of a driving force of an electric motor to protract and retract a seatbelt.
An example of the automotive passenger restraint and protection apparatus provided with such an electric retractor is disclosed by Japanese Laid-Open Patent Publication (Kokai) No. 59-45240, which is adapted to control the driving of the electric motor based upon an output from a displacement detecting device which detects displacement of the seatbelt in retracting and protracting directions as well as an output from an attaching detecting device which detects attaching of the seatbelt to the occupant's body.
The electric retractor, however, requires the displacement detecting device which is expensive, and therefore has an increased manufacturing cost and a complicated construction.
Further, the rotation control of the electric motor of the electric retractor is carried out by applying constant voltage of negative and positive signs to the motor to cause normal rotation and reverse rotation of the motor, as disclosed by Japanese Laid-Open Utility Model. Publication (Kokai) No. 61-134464.
According to the known electric retractor, however, since the motor is rotated in the normal direction or in the reverse direction depending upon the application of the constant voltage, there is a possibility that in retracting the seatbelt, the seatbelt is suddenly wound up by the motor so that a tongue of the seatbelt hits against a side window pane.
Another electric retractor is disclosed by Japanese Laid-Open Patent Publication (Kokoku) No. 3-79212, in which a retracting force is stored in a return spring (second retracting force generating device) utilizing the protracting motion of the seatbelt, and when the motor output drops below a predetermined value such that the motor cannot retract the seatbelt, for example, due to failure of an electrical system for driving the motor (first retracting force generating device), or a drop in the motor torque due to a drop in the electromotive force of a battery installed in the automotive vehicle, a rotative force transmission device transmits the retracting force stored in the return spring to a takeup shaft of the seatbelt. This assures retraction of the seatbelt even when the seatbelt cannot be wound up by the motor.
According to this retractor, however, the motor (first retracting force generating device) or the return spring (second retracting force generating device) is selected to retract the seatbelt by the rotative force transmission device, that is, the two devices are not simultaneously used for retraction of the seatbelt which requires designing each of the motor and the return spring so as to produce a strong retracting force by itself.
Besides, in the retractor, if the retracting force of the motor becomes weakened due to aging change, etc. so that the motor cannot fully retract the seatbelt, the motor is switched to the return spring for retracting the seatbelt. However, in fact the retracting force of the motor is merely weakened but not reduced to zero. Therefore, if the motor is switched to the return spring for retracting the seatbelt, the retracting force remaining in the motor cannot be fully utilized.
An automotive passenger restraint and protection apparatus is also known from Japanese Laid-Open Patent Publication (Kokai) No. 9-82171, which turns on or off a switch for detecting an amount of retraction of a seatbelt on a reel shaft, depending upon the thickness of a portion of the seatbelt wound on the reel shaft, to thereby detect an amount of protracting of the seatbelt or the amount of retraction of the same, to use the detected value in controlling an electric circuit for warning the occupant of failure to fasten the seatbelt or in controlling a seatbelt locking mechanism provided in a seatbelt retractor.
In the seatbelt retraction detecting switch, however, since the amount of protraction or amount of retraction of the seatbelt is detected by turning-on or turning-off of the seatbelt retraction amount detecting switch, only information as to whether the seatbelt has been wound up or pulled out by a predetermined amount or more can be obtained, and a specific value of the protracting amount or retraction amount cannot be obtained.